The present invention generally relates to devices for cooling livestock and more specifically to a gear drive fan for ventilating and cooling a livestock structure. The subject gear driven fan may be implemented alone, or combined with means for injecting water droplets into the air stream of the fan blade and/or means for oscillating the fan assembly through a plurality of rotational positions.
It is known in animal agriculture to cool livestock with evaporative cooling by wetting the animal and then drying the animal through mechanical ventilation or via natural ventilation. Mechanical ventilation is often provided by cooling fans. The cooling fans typically have blade diameters of thirty-six inches and larger, with forty-eight inch diameter being a common size. Depending upon the temperature and humidity, it is often necessary to move a large volume of air to adequately cool the livestock.
Two types of fans are known to be used for cooling livestock. The first type is a belt drive fan, such as disclosed in U. S. Pat. No. 4,693,852. In this type of cooling fan, a motor powers a belt and pulley to rotate the fan blades. The second type is a direct drive fan, where the fan blades are mounted directly to the motor shaft. Each type has its advantages and disadvantages.
The blade of a direct drive fan rotates at the same RPM as the motor shaft, typically 1170 RPM or 1750 RPM. High blade speeds result in excessive noise. Moreover, running fan blades at high speeds is inefficient. Air flow increases linearly with an increase in RPM, according to the equation CFM1/CFM2=RPM1/RPM2. However, horsepower requirements increase with the cube of the RPM, according to the equation HP1/HP2=(RPM1/RPM2)3. Another disadvantage, particularly for large diameter fans, is that any wind or other phenomena which slows or reverses the blades may result in harmful torque to the motor. Lower fan speeds reduce potential damage to the motor from harmful torque.
The belt drive system allows a blade speed slower than the shaft speed of the motor, resulting in lower power requirements and noise levels. Belt drive fans also allow changing the blade speed of the fan by changing pulley size on either the motor shaft or blade shaft. However, belt drive fans have their own disadvantages. Belt slippage causes a decrease in air flow in the fan which can result in morbidity and/or mortality in livestock, particularly in poultry houses. Belt drive systems require regular maintenance, and belts must frequently be replaced. It is not uncommon for a belt drive fan to throw a belt resulting in the fan being taken out of service, potentially for a long period of time. Belt drive systems also require additional parts such as shafts and bearings, none of which are particularly suited to a humid or wet environment. Most belt drive systems, such as that disclosed in U. S. Pat. No. 4,693,852, have the motor and belts contained within the same enclosure as the fan blades, requiring the enclosure to be opened to gain access to the belts.
The present invention is directed to a gear drive fan for ventilating and cooling structures used for containing livestock. The disclosed gear drive fan comprises a livestock structure having a roof and supporting members, where the roof is connected to the supporting members, a fan assembly, and means for attaching the fan assembly to the structure. The fan assembly comprises a blade assembly having a plurality of blades and a drive hub, a housing, a first electrical motor having a drive shaft, and a gearbox having a drive end and a hub end. The drive end of the gearbox is adapted to be closely coupled to the drive shaft of the motor, while the hub end is adapted to be closely coupled to the drive hub of the blade assembly, so that the motor and gearbox may be conveniently mounted to the housing or contained within the housing. The blades radiate outwardly from the hub, such that the blades create an air stream upon rotation of the blade assembly. The means for attaching the fan assembly to the structure include an wall-mounted or ceiling-mounted box enclosure, an oscillating enclosure, and an enclosure which is suspended by an adjustable hanger connected to a support member of the livestock structure.
In another embodiment, the gear drive fan further comprises means for injecting water droplets into the air stream of the fan blade.
In another embodiment, the motor may be connected to a variable frequency drive for even further speed control of the fan blades.
These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings.